Distance-dependent fluorescence of tris(bipyridine)ruthenium(ii) on supported plasmonic gold nanoparticle ensembles

What is it about?

Metallic surfaces and particles can interact with fluorescent species, and modify their properties. Here, we used Au NP films, coated with dielectric layers of tunable thicknesses, and topped with a monolayer of the fluorophore tris(bipyridine)ruthenium(II). We found multiple distance-dependent effects, with a long-range interaction, mediated by thin-film interference, as we explored in previous work. We found that the NP film can quench the emission for very close NP-fluorophore separations (~2 nm), but enhances its magnitude (by a factor of 4-5) for longer separations, up to hundreds on nanometers. This is a result of the NPs interacting and acting as a far-field mirror; individual NPs only interact with fluorophores up to a distance of a few tens of nanometers. The radiative lifetime of the fluorophore is shortened due to the interaction. We also observed an effect previously predicted in theory studies, but not shown experimentally - the emission wavelength and peak widths were modified by the interaction.

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